The present invention relates generally to the field of reducing pollutant emissions produced by combustion engines, and more specifically to the conversion of otherwise wasted mechanical energy to electrical energy for the operation of exhaust aftertreatment devices.
In a wide variety of applications, notably vehicular applications, aftertreatment devices are used to reduce the level of pollutants in combustion engine exhausts. Such aftertreatment devices usually require energy for operation, either continuously to support a primary mode of operation, or sporadically to support a maintenance operation. For example, a non-thermal plasma converter requires power continuously to produce a plasma arc that effects pollutant conversion; a particulate trap, in contrast, requires power only sporadically to incinerate accumulated deposits.
Conventionally, powering these aftertreatment devices often reduces the overall efficiency of the vehicle. For the non-thermal plasma converter, an alternator attached to the engine drive shaft diverts otherwise useful power to the converter. For the particulate trap, the engine may be run sporadically at an inefficient high temperature to effect deposit incineration.
In conventional vehicle operation, however, mechanical energy in various forms is temporarily stored, but then typically wasted. For example, engine exhaust energy not consumed running a turbo charger is typically ducted overboard; vehicle kinetic energy not consumed climbing hills is typically dissipated during braking. An opportunity exists, therefore, to increase overall vehicle efficiency by using otherwise wasted mechanical energy to power exhaust aftertreatment devices.
The opportunity described above is addressed, in one embodiment of the present invention, by an apparatus for reducing emissions of a combustion engine, the apparatus comprising: an energy converter adapted to convert mechanical energy to electrical energy, the energy converter having no mechanical coupling to any drive shaft of the combustion engine; and an exhaust aftertreatment device adapted to receive electrical energy from the energy converter, receive exhaust gases from the combustion engine, and remove pollutants from the exhaust gases.